Methods of forming a layered article

ABSTRACT

A method of forming a layered article, the method comprises thermoforming a substrate sheet to form a shaped substrate, wherein the shaped substrate is a fiber-reinforced plastic material having a void content sufficient to allow a vacuum to be applied through the shaped substrate; pulling a vacuum through the shaped substrate; and pulling a film layer onto a surface of the shaped substrate to form the layered article.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims priority to Provisional U.S. PatentApplication No. 60/539,188 filed Jan. 26, 2004, which is herebyincorporated by reference in its entirety.

BACKGROUND

Market economics for aesthetic composite structures comprising asubstrate and an aesthetic surface layer often favor use ofthermosetting resin systems for the substrate. Low raw material andtooling costs are frequently cited as factors supporting selection ofthermosetting materials. However, use of thermosetting materials canproduce volatile organic compound (VOC) emissions, and generally resultsin long cycle times.

For example, one commonly used approach for creating aesthetic partsinvolves a two step procedure, wherein a thermoplastic surface layer isformed using a traditional thermoforming method, a thermosettingmaterial is injected or sprayed behind this surface layer and is curedin-place to create a bi-layered structure having a reinforced sub-layerand a thermoplastic surface layer. Many thermosetting systems andmethods are employed to create the reinforced sub-layer. These include,for example, spray-up fiberglass reinforced plastic (FRP), resintransfer molding, vacuum-infusion, and various reinforced foam in-placetechnologies.

What is needed in the art is a method of making a layered article thatproduces lower VOC emissions and has a shorter cycle time compared tocurrent methods employing a thermosetting step.

SUMMARY

An embodiment of a method of forming a layered article comprisesthermoforming a substrate sheet to form a shaped substrate, wherein theshaped substrate is a fiber-reinforced plastic material having a voidcontent sufficient to allow a vacuum to be applied through the shapedsubstrate; pulling a vacuum through the shaped substrate; and pulling afilm layer onto a surface of the shaped substrate to form the layeredarticle

Another embodiment of a method of forming a layered article comprisesheating a substrate sheet to a temperature sufficient to allow loftingof fibers of the substrate sheet; disposing the substrate sheet againsta membrane assisted pressure box; pushing the substrate sheet onto amold to form a shaped substrate; heating a film layer; disposing thefilm layer adjacent to shaped substrate; pulling a vacuum through theshaped substrate; and pulling the film layer against the shapedsubstrate to form the layered article.

The above-described and other features will be appreciated andunderstood by those skilled in the art from the following detaileddescription, drawings, and appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Refer now to the figures, which are exemplary embodiments, and whereinthe like elements are numbered alike.

FIG. 1 is a cross-sectional side view of a matched tool with anexemplary substrate to be thermoformed.

FIG. 2 is a cross-sectional side view of a membrane assistedvacuum/pressure equipment with an exemplary substrate to bethermoformed.

FIG. 3 is a cross-sectional side view of a vacuum thermoforming systemwith a film layer to be thermoformed over a shaped substrate.

FIG. 4 is a cross sectional view of an exemplary plastic layeredarticle.

DETAILED DESCRIPTION

Disclosed herein are methods for making plastic layered articles havinga substrate with an open-celled structure. It should be noted that, asused herein, the term “open-celled” has its ordinary meaning, anddescribes cells in fluid communication with adjacent cells such thatfluid communication is established from one surface through to anopposite surface. The term “thermoforming” and its various derivativeshave their ordinary meaning, and are used herein to generically describea method of heating and forming a sheet into a desired shape.Thermoforming methods and tools are described in detail in DuBois andPribble's “Plastics Mold Engineering Handbook”, Fifth Edition, 1995,pages 468 to 498.

The term “layer” is used herein for convenience, and includes materialshaving an irregular shape as well as sheets and films. It should furtherbe noted that the terms “first,” “second,” and the like herein do notdenote any order, quantity, or importance, but rather are used todistinguish one element from another, and the terms “a” and “an” hereindo not denote a limitation of quantity, but rather denote the presenceof at least one of the referenced item. Furthermore, all rangesdisclosed herein are inclusive and combinable (e.g., ranges of “up toabout 25 weight percent (wt.%), with about 5 wt.% to about 20 wt.%desired, and about 10 wt.% to about 15 wt.% more desired,” is inclusiveof the endpoints and all intermediate values of the ranges, e.g., “about5 wt.% to about 25 wt.%, about 5 wt.% to about 15 wt.%,” etc.).

The methods disclosed herein are of particular utility in themanufacture of layered articles comprising a thermoformable film layerdisposed on an open-celled, fiber-reinforced thermoformable substrate.The film layer can function as a surface layer for the substrate, and isselected to be both thermoformable and compatible with the substrate. Inone embodiment, the film layer is an aesthetic layer. In variousembodiments, the film layer can include several layers, e.g., the filmlayer may comprise a surface layer and a compatible layer. It should benoted that the term “film layer” is used throughout this disclosuremerely for convenience, and may refer to embodiments wherein the filmlayer is single-layered or embodiments where it comprises severallayers. Moreover, the materials listed with regard to the film layer maybe the same materials employed in the compatible layer. If the filmlayer comprises an additional layer, e.g., a compatible layer, it is tobe understood that the additional layer is compatible with any otherlayer making up the film layer, the substrate, and any other layersadjacent to the compatible layer.

Further, the substrate and the film layer can comprise the same ordifferent plastic materials that are compatible with each other. As usedherein, “compatible” means that the layers are capable of being joined,and do not adversely interact with each other. The plastic materials cancomprise thermoplastic materials, thermoset materials, as well ascombinations comprising at least one of the foregoing plastic materials.Exemplary thermoplastic materials include polypropylene, polycarbonate(PC), polyester, polyetherimide (PEI), polyarylene ethers, and the like,as well as combinations comprising at least one of the foregoingthermoplastic materials, for example PC/PET blends. Suitablethermoplastic polyesters include, for example, poly(alkylenedicarboxylates) such as poly(ethylene terephthalate) (PET),poly(1,4-butylene terephthalate) (PBT), poly(trimethylene terephthalate)(PTT), poly(ethylene naphthalate) (PEN), poly(butylene naphthalate)(PBN), poly(cyclohexanedimethanol terephthalate),poly(cyclohexanedimethanol-co-ethylene terephthalate) (PETA), andpoly(1,4-cyclohexanedimethyl-1,4-cyclohexanedicarboxylate) (PCCD);poly(alkylene arenedioates); and combinations comprising at least one ofthe foregoing polyesters.

In an exemplary embodiment, the substrate and film layer each comprise apolycarbonate. Linear or branched aromatic polycarbonates may be used.In one embodiment, polycarbonates comprising units derived from one ormore of 2,2-bis(4-hydroxyphenyl)propane (“Bisphenol A”),bis(2-hydroxyphenyl)methane,1,1-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane, fluorenonebisphenol, 1,1-bis(4-hydroxyphenyl)ethane, 2,6-dihydroxynaphthalene,bis(3,5-diethyl-4-hydroxyphenyl)sulfone,2,2-bis(3,5-dibromo-4-hydroxyphenyl)propane, 4,4′-dihydroxydiphenylether, spiro biindane bisphenol, and the like, may be used.

Exemplary thermoset materials include thermosetting resins such asepoxy, phenolic, alkyds, polyester, polyimide, polyurethane, mineralfilled silicone, bis-maleimides, cyanate esters, vinyl, andbenzocyclobutene resins, in addition to blends, copolymers, mixtures,reaction products and composites comprising at least one of theforegoing.

The plastic materials of the substrate comprise sufficient bondingcapability to provide sufficient structural integrity to the substrateto enable thermoforming thereof. For example, the substrate can comprisefibers and thermoplastic material(s) such that the substrate can bedisposed in a thermoforming system and thermoformed. In anotherexemplary embodiment, the substrate can comprise fibers, thermosettingmaterial(s), and an agent wherein the agent retains the structure of thesubstrate in the desired form (e.g., a sheet) such that the substratecan be disposed in a thermoforming system and thermoformed.

Depending on the particular end use of the article, the substrate and/orthe film layer may include one or more additives for the provision orenhancement of a visual effect. Such visual additives include, but arenot limited to, pigments and decorative material such as metal flakes,dyes, and luminescent compounds. Specific examples of suitable additivesinclude metallic oxides (such as titanium dioxide and iron oxide); metalhydroxides; metal flakes (such as aluminum flake); chromates (such aslead chromate); sulfides; sulfates; carbonates; carbon black; silica;talc; china clay; phthalocyanine blues and greens, organo reds; organomaroons and other organic pigments and dyes, and the like, as well ascombinations comprising at least one of the foregoing visual additives.In an exemplary embodiment, pigments that are stable at hightemperatures are used, i.e., colorants that do not substantially degradeor alter at temperatures at or about 350° C.

Light fastness additives may also be present in the film layer and/orsubstrate, again depending on the particular end use of the article. Forexample, the film layer and/or substrate may further comprise a lightfastness compound, a light fastness antioxidant, and/or a light fastnessozonant. Examples of light fastness compounds includedidodecyl-3,3′-thio dipropionate,tris(4-tert-butyl-3-hydroxy-2,6-dimethyl benzyl)isocyanurate,1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene,N,N′-beta,beta′-naphthalene-4-phenylene diamine,4,4′-methylene-bis(dibutyl dithio-carbamate),2,2,4-trimethyl-1,2-hydroquinoline, and the like.

In addition or alternative to the above additives, property additivesmay be used in the film layer and/or substrate. Exemplary propertyadditives include impact modifiers, UV absorbers, flame retardants,fillers, stabilizers, ester interchange inhibitors, adhesion promotingagents such as a bisphenol derivative, an aminosilane or derivativesthereof, mold release agents, and the like, as well as combinationscomprising at least one of these proposed additives. Examples ofultraviolet light absorbers (UVA) include benzotriazole, benzophenone,triazine, cyanoacrylate, dibenzoylresorcinol, benzoxazinone, and thelike as well as hindered amine light stabilizers (HALS) such as2-(benzotriazol-2-yl)-4-(1,1,3,3-tetramethylbutyl)phenol,2-(benzotriazol-2-yl)-4-methylphenol, 2-hydroxy-4-octyloxy benzophenone,2-hydroxy-4-methoxybenzophenone, ethyl-2,2-diphenyl-1-cyanoacrylate,2-(2′-hydroxy-4′-octyloxy) bis-4,6-(2′,4′-dimethylphenyl)triazine,2-ethyl-2′-ethoxy oxalanide, bis[2-hydroxy-5-methyl-3-(benzotriazol-2-yl) phenyl]-methane, and the like.Combinations comprising one or more of any of the above additives mayalso be used.

Furthermore, with regard to the substrate, it is a fiber-reinforcedplastic material having a porosity sufficient for a vacuum to be appliedtherethrough after thermoforming. It is noted that the porosity of thesubstrate may be defined in terms of the void content of the substrate.More particularly, the thermoformed substrate (i.e., a shaped substrateformed by a thermoforming method) can have a void content greater thanor equal to about 5 volume percent (vol.%), specifically a void contentof about 10 vol.% to about 50 vol.%, more specifically, a void contentof about 25 vol.% to about 50 vol.%, wherein the volume percents arebased on the total volume of the substrate. For example, the substratecan be an open-celled, fiber-reinforced plastic material. Alternatively,the substrate can be a foraminated, fiber-reinforced plastic material(e.g., openings can be punched, drilled, formed, stamped, or otherwisedisposed through the substrate and/or shaped substrate). The term“foraminate” has its ordinary meaning, and is used herein to refer to asubstrate that has holes physically disposed therein. It is to beunderstood by those skilled in the art that an open-celled structure canbe construed to have “holes”, e.g., cells in fluid communication withadjacent cells such that fluid communication is established from onesurface through to an opposite surface. However, the term “foraminated”is used throughout this disclosure merely for convenience to discusssystems having holes other than those formed by a network of cells influid communication with each other.

The fibers employed in the substrate are selected such that afiber-reinforced plastic is formed, and optionally an open-celledfiber-reinforced plastic material. Fiber type, size, amount, and thelike may vary with the plastic material employed in making thesubstrate. In an exemplary embodiment, the fibers are selected to impartthe desired void volume to the substrate. In order to attain the desiredmold replication and a desired void volume, the fibers can be capable oflofting (e.g., of expanding in the z-direction when heated). Exemplaryfiber types include, but are limited to, glass fibers (e.g., E-glass(“electrical glass”, e.g., borosilicate glass), S-glass (“structuralglass”, e.g., magnesia/alumina/silicate glass), and the like), mineralfibers, polymer fibers, natural fibers, and the like, as well ascombinations comprising at least one of the foregoing fibers.Optionally, the fiber diameter (width) may be about 6 micrometers toabout 25 micrometers. Optionally, the fiber length may be about 2millimeters (mm) to about 75 mm.

The fiber-reinforced plastic material of the substrate comprises asufficient amount of plastic material and fibers to provide the desiredstructural integrity and void volume to the substrate. For example, thefiber-reinforced plastic substrate can comprise about 25 weight percent(wt. %) to about 75 wt. % plastic material, specifically about 35 wt. %to about 65 wt. %, and more specifically about 40 wt. % to about 60 wt.% plastic material may be employed. About 25 wt. % to 75 wt. % fiberswith the plastic material, specifically about 35 wt. % to about 65 wt. %and more specifically about 40 wt. % to about 60 wt. % fibers may beused. The weight percents are based on the total weight of thefiber-reinforced plastic substrate.

Examples of suitable commercially available substrate materials include,but are not limited to, AZDEL® SuperLiteg and AZDEL® Glass MatThermoplastics (GMT), which are available from AZDEL, Inc., Shelby,N.C., having various matrices including, but not limited to,polyproplylene, polycarbonate (e.g., LEXAN® from General ElectricCompany), polyester (e.g., VALOX® from General Electric Company),polyetherimide (e.g., ULTEM® from General Electric Company), polyaryleneether (e.g., polyphenylene ether; PPO® Resin from General ElectricCompany), polystyrene, polyamide and/or combinations comprising at leastone of the foregoing.

For example, the substrate may be produced according to the WigginsTeape method (e.g., as discussed in U.S. Pat. Nos. 3,938,782; 3,947,315;4,166,090; 4,257,754; and 5,215,627). For example, to produce a mataccording to the Wiggins Teape or similar method, fibers, thermoplasticmaterial(s), and any additives are metered and dispersed into a mixingtank fitted with an impeller to form a mixture. The mixture is pumped toa head-box via a distribution manifold. The head box is located above awire section of a machine of the type utilized for papermaking. Thedispersed mixture passes through a moving wire screen using a vacuum,producing a uniform, fibrous wet web. The wet web is passed through adryer to reduce moisture content and, if a thermoplastic is used, tomelt the thermoplastic material(s). A non-woven scrim layer may also beattached to one side or to both sides of the web to facilitate ease ofhandling the substrate (e.g., to provide structural integrity to asubstrate with a thermoset material). The substrate can then be passedthrough tension rolls and cut (guillotined) into the desired size.

Optionally disposed between the substrate and film layer can be a tie-layer. Use of a tie-layer can provide enhanced bonding, by increasingthe amount of resin at the interface, and or by improving thecompatibility between the film layer and the substrate layer,particularly where these layers comprise different resins. The tie-layercomprises a material that is selected to be compatible with the filmlayer and the substrate. Specific examples of compatible materials foruse in the tie-layer include polycarbonates; polyesters such as PET,PBT, PTT, PEN, PBN, PETA and PCCD; polyetherimides; polyamides;polyalkylene arenedioates; polyacrylonitrile-containing resins such as,for example, ABS, ASA, or acrylonitrile-(ethylene-polypropylene diaminemodified)-styrene (AES); phenylene sulfide; polymethyl methacrylate(PMMA); copolyester carbonates; poly(alkylene dicarboxylates); or thelike; or combinations comprising at least one of the foregoing polymers.In one embodiment, the tie-layer comprises a blend of a resin from thefilm layer and a resin from the substrate layer.

Polycarbonates and blends of polycarbonates with polyesters may beadvantageously be used in the tie-layers, particularly in combinationwith film layers comprising the arylate polyester resins as describedabove. As is known, polycarbonates possess recurring structural units asshown in the following formula:

wherein R¹ is as defined above. Suitable polycarbonate resins includelinear aromatic polycarbonate resins, for example those based comprisingunits derived from bisphenol A, and branched aromatic polycarbonateresins.

Polyesters and blends comprising two or more of polyesters may also beadvantageously be used in the tie-layer, particularly in combinationwith film layers comprising the arylate polyester resins as describedabove. For example, one suitable blend for use in the tie-layercomprises, based on the weight of the blend, about 10 wt. % to about 50wt. % of PBT, PET, glycolized poly(ethylene terephthalate),poly(cyanoterephthalydene) (PCT), PCTA or PCTG and about 50 wt. % toabout 90 wt. % of an arylate polyester resin, specifically a resorcinolpolyester resin as described above and about 50 wt. % to about 90 wt. %of a resin comprising resorcinol arylate units.

The thermoformable film layer and/or the tie-layer may be producedseparately by methods such as molding, extrusion, coating, casting,vacuum deposition, or the like. The layers may then be adhered using anadhesive and/or laminated. In applications wherein the laminate is inthe form of a film for subsequent disposal on a pre-formed substrate,the tie-layer may serve as a reinforcement to facilitate the handling ofthe film layer, which may have relatively little inherent tensilestrength.

Alternatively, the thermoformable film layer and the tie-layer may beproduced in the form of a laminate by co-injection molding,co-extrusion, overmolding, coating, or the like. For example, the filmlayer and tie-layer (and other optional layers) may be extruded fromseparate extruders through separate sheet dies into contact with oneanother when hot, and then passed through a single sheet of rollers. Inanother embodiment, the polymer melts of the materials constituting thefilm layer, the optional tie-layer or layers, and other optional layersmay be brought together and into contact with one another through aco-extrusion adapter/feed block and then through a single ormulti-manifold die. The adapter/feed block is constructed such that themelts forming the separate layers are deposited as adherent layers onthe melt of the center layer. After co-extrusion, the multilayer lengthof the melt produced can be formed into desired shapes; solid sheets ormulti-wall panels, in an extrusion die connected downstream. The melt isthen cooled under controlled conditions in known manner by means ofcalendaring (solid sheet) or vacuum sizing (multi-wall panel) andsubsequently cut into lengths. An annealing oven may be optionallyprovided after sizing or calendaring for the reduction of stresses.

In accordance with the present method, the substrate is thermoformedinto a shape substantially corresponding to the shape of the desiredfinal article. Generally, thermoforming comprises the sequential orsimultaneous heating and forming of a material onto a mold, wherein thematerial is originally in the form of a sheet and is formed into adesired shape. Once the desired shape has been obtained, the formedarticle is cooled below its solidification or glass transitiontemperature. Generally, any thermoforming method capable of producing aformed substrate having a void content sufficient to enable a vacuum tobe pulled therethrough, e.g., a void content of greater than or equal toabout 5 vol. % may be employed. For example, suitable thermoformingmethods include, but are not limited to, mechanical forming (e.g.,matched tool forming), membrane assisted pressure/vacuum forming,membrane assisted pressure/vacuum forming with a plug assist, and thelike.

In a matched tool forming method of forming the substrate, a substrateis heated at a sufficient temperature and for a sufficient time to allowthe substrate to reach a softening temperature (which may also bereferred to as a forming temperature) such that the substrate may bephysically worked (i.e., work-formed) into a desired shape. It is notedthat the substrate may be heated in various fashions, such as in radiantthermoforming ovens (which may include a top and/or bottom heater). Thesubstrate is then disposed between a male forming tool and a femaleforming tool. The male and female forming tools are brought in physicalcontact with each other via stops (disposed at a peripheral edge of eachtool) under a pressure sufficient to form the substrate into the desiredshape, while maintaining void contents in the ranges previouslymentioned. Suitable pressures will depend on the particular substratecomposition, and are readily determined by one of ordinary skill in theart without undue experimentation. However, it is noted that use ofexcessive pressure is to be avoided, as it may close some or all of thecells thereof to below a desired void content, rendering the substrateinsufficiently porous.

Referring now to FIG. 1, a cross-sectional view of a matched toolforming is provided. A heated substrate sheet 10 is held in positionrelative to a male forming tool 12 and female forming tool 14 usingclamps 16. It is noted that the male forming tool 12 and the femaleforming tool 14 are configured to “match”, i.e., complement, each other.The male forming tool 12 and the female forming tool 14 may optionallycomprise a plurality of holes 18 and 20 respectively. Disposed at aperiphery of male forming tool 12 and female forming tool 14 are stops(spacers) 22 and 24 respectively, which are used to determine thethickness of the shaped substrate. The stops 22 and 24 are positionedoutside of the forming area. The male tool 12 and female tool 14 areconstructed of materials that are compatible with the substratematerials. For example, the tool may be constructed of, but not limitedto, the following materials: aluminum, steel, epoxy, silicone rubber,filled tooling resin, and the like.

During forming, the substrate is heated to a temperature sufficient toallow thermoforming and desirably sufficient to allow lofting of thefibers in the substrate. For example, a temperature of about 450° F.(about 232° C.) to about 700° F (about 371° C.), more specifically,about 550° F. (about 288° C.) to about 650° F. (about 343° C.), issuitable for thermoforming a glass fiber-reinforced polycarbonatesubstrate sheet. The heated substrate is then formed by creatingrelative motion between the male tool 12 and female tool 14, such thatstops 22 contact stops 24. Bringing the male tool 12 together with thefemale tool 14 with the substrate sheet 10 therebetween causing thesubstrate sheet 10 to conform to the shapes of the male and female tools12, 14. The substrate can then be cooled to form a shaped substrate. Apressure of about 1 atmosphere (about 101 kPa) to about 10 atmosphere(about 1013 kPa), more particularly about 1 atmosphere (about 101 kPa)to about 5 atmosphere (507 kPa) is employed to form the AZDEL®SuperLite® substrate.

In a membrane-assisted vacuum/pressure forming method, a heatedsubstrate is disposed against a pressure box. Vacuum and pressure aresimultaneously applied to the substrate. More particularly, a vacuum ispulled through a forming tool and positive pressure is applied to theside of the membrane opposite the side closest to the forming tool. Thedirection of the vacuum and pressure are indicated schematically in theFIG. 2 by arrows. The vacuum applied through the mold causes the sheetto be pulled into/onto (hereinafter onto) the mold. Suitable pressures(positive and negative) will depend on the particular substrate and arereadily determined by one of ordinary skill in the art without undueexperimentation. Further, as noted above, excessive pressure is to beavoided, as it may close some or all of the cells, rendering thesubstrate insufficiently porous.

FIG. 2 schematically illustrates a membrane assisted vacuum/pressurethermoforming method. A heated substrate 26 is disposed between apressure box 28 and a forming tool 30. While forming tool 30 may be amale forming tool or a female forming tool, the forming tool 30 isillustrated as a male forming tool. Forming tool 30 comprises holes 32such that a vacuum may be applied through the forming tool 30. Clamps 34may be used to hold the substrate sheet in position relative to thepressure box 28 and the forming tool 30. A membrane 36, morespecifically, a non-permeable membrane, is stretched across the openingof the pressure box 28. As discussed above, a first surface 26A of thesubstrate 26 is brought in physical contact with forming tool 30 via avacuum being pulled through the forming tool 30, while a second surface26B is brought in physical contact with membrane 36. A pressure isapplied to the membrane 36 from membrane side 36B. Since substrate is anopen-celled, fiber-reinforced thermoplastic material having a voidcontent greater than or equal to about 5 vol. % as discussed above, avacuum is pulled directly through the substrate 26. As such, themembrane 36 is employed to push the substrate onto the forming tool 30(i.e., a vacuum is pulled through the substrate 26 and pulls membrane 36and therefore substrate 26 toward tool 30 as the positive pressure frompressure box 28 pushes the membrane 36 toward to tool 30). In otherwords, a vacuum cannot be pulled through the membrane 36. Rather, thevacuum pulls the membrane 36 toward the forming tool 30 as pressureapplied to the membrane 36 pushes the membrane 36 toward the formingtool 30. Once the substrate is on the forming tool 30, it is cooled toform the shaped substrate.

For example, if AZDEL® SuperLite® is the substrate, a pressure of about1 atmosphere (about 101 kPa) to about 5 atmospheres (about 507 kPa) maybe applied to the membrane 36 to push the substrate 26 toward formingtool 30, while a vacuum is being pulled through forming tool 30. Moreparticularly, about 1 (about 101 kPa) atmosphere to about 3 atmospheres(about 304 kPa) of pressure may be applied to the membrane 36.

The above described thermoforming methods are provided merely forexemplary purposes. It is to be understood that the substrate may beformed by any thermoforming method, wherein the resulting moldedsubstrate has a void content such that a vacuum may be applied throughthe substrate.

After thermoforming the substrate to produce a shaped substrate, theshaped substrate may optionally be trimmed to substantially the finalshape of the desired article. The trimming may occur prior to orsubsequent to disposing of the film layer on the shaped substrate. Thetrimming method may include, for example, laser trimming, water jettrimming, trim press trimming, and the like, as well as combinationscomprising at least one of the foregoing methods.

Deposition of the film layer onto the shaped substrate comprises usingthe shaped substrate as the forming tool to pull the film layer onto theshaped substrate. Therefore, once formed, the shaped substrate canremain on the forming fool to receive the film layer or be moved to adifferent forming tool. Although the shaped substrate may be usedwithout a forming tool, it is desirable to employ the forming tool forstructural integrity. During application of the film layer onto theshaped substrate, the film layer is heated in a similar manner asdescribed above for the substrate, and is held in position relative tothe holding fixture and substrate using, for example, clamps. A vacuumis then pulled through the shaped substrate to pull the film layer ontothe substrate to form a layered article. In various embodiments, atie-layer may be introduced between the substrate and the film layer toimprove adhesion between the substrate and the film layer. When atie-layer is employed, it is disposed on the film layer, between theshaped substrate and the film layer, before the film layer isthermoformed onto the shaped substrate, such that, when the film layeris pulled onto the shaped substrate, the tie-layer is also pulled on(and possibly extrudes into) the shaped substrate. This tie-layer canassist in bonding the shaped substrate and the film layer together.

Referring now to FIG. 3, a cross-sectional side view of a vacuumingforming apparatus with the substrate is illustrated. A shaped substrate38 is placed on a male forming tool 40 comprising a plurality of holes42. A film layer 44 in the form of a sheet is heated, and held inposition relative to the shaped substrate 38 and the male forming tool40 via clamps 46. A vacuum is pulled through the forming tool 40 asillustrated in the drawing by an arrow. Since the shaped substrate 38has a sufficient porosity to allow a vacuum to be pulled through it, thesurface layer 44 is pulled onto the formed substrate 38 to form thelayered article. It is noted that in various embodiments, the layeredarticle may be trimmed, e.g., on the male forming tool 40 by anytrimming method, e.g., those trimming methods discussed above.

An exemplary shaped multilayer article 110 obtainable by the presentmethod is shown in FIG. 4, and comprises a film layer 112 and asubstrate 114. The film layer 112 can function as a surface layer forthe substrate, and is selected to be both thermoformable and compatiblewith the substrate. In one embodiment, the outer surface of the filmlayer 112 may be configured with surface designs, and/or may containadditives that can provide optical effects.

As is further shown in FIG. 4 an optional first compatible layer 116,which may comprise additives that can provide optical effects, may bedisposed between film layer 112 and substrate 114. Where optional firstcompatible layer 116 is used to provide an optical effect, film layer112 may be clear. The combination of film layer 112 and first compatiblelayer 116 is often referred to as an aesthetic layer, and is shown inFIG. 4 as 118.

A tie-layer 120 may further be disposed between substrate 114 andoptional first compatible layer 116 or film layer 112. Tie-layer 120 maybe used to increase bonding between the layers. Where no tie-layer ispresent, optional first compatible layer may function to increasebonding between film layer 112 and substrate 114.

An optional balance layer 122 may be disposed on a side of substrate 114opposite film layer 112. The purpose of balance layer 122 is to providea layer on a side of substrate 114 opposite film layer 112 that matchesthe coefficient of thermal expansion of film layer 112. A secondtie-layer 124 may be disposed between substrate 114 and balance layer122. In addition, a second compatible layer may be disposed betweenbalance layer 122 and tie-layer 124 or substrate 114 (not shown). It isto be understood that article 110 may be provided in any desired shape,which will be dictated by the end use of the article.

Structural articles formed using the materials and methods disclosedherein may include any use where a layered plastic article may beadvantageous. For example, articles include but are not limited to,exterior and interior components for aircraft, automotive (e.g., cars,trucks, motorcycles, and the like). For example, various componentsinclude, but are not limited to panels, quarter panels, rocker panels,vertical panels, horizontal panels, fenders, head liners, doors, and thelike.

Advantageously, the methods disclosed herein simplify the production ofunpainted, cosmetic, structural parts and panels compared to methodsemploying thermosetting materials. In various embodiments, theproduction of these parts can proceed on a single forming station withgreater efficiency than is currently possible. Methods that usethermoforming have required a separate, non-thermoforming step todispose the substrate or sub-layer onto a shaped layer (e.g., a shapedfilm layer), e.g., by spraying, injecting, or the like. However, byemploying a substrate with a sufficient void volume to enable a vacuumto be pulled through the shaped substrate to pull another layer ontothat substrate, the film layer can also be applied using thermoforming.Since the shaped substrate can be formed on a male or female mold, thesubsequent layer (e.g., film layer) can be an aesthetic layer applied toan outer surface of the shaped substrate.

This method reduces the types of equipment used to produce these layeredproducts and can decrease formation time and simplify the layeredarticle manufacturing process. In addition, when this thermoformingmethod does not employ a thermosetting material, VOC emissions aregreatly reduced, if not eliminated, compared to other method using athermosetting material. The relatively low pressures that are employedin the methods disclosed herein also allows for relatively low toolingcosts. Finally, the porous nature of the underlying substrate structurehelps reduce thermo-elastic stresses that arise during the attachment ofthe surface layer.

While the invention has been described with reference to an exemplaryembodiment, it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted forelements thereof without departing from the scope of the invention. Inaddition, many modifications may be made to adapt a particular situationor material to the teachings of the invention without departing from theessential scope thereof. Therefore, it is intended that the inventionnot be limited to the particular embodiment disclosed as the best modecontemplated for carrying out this invention, but that the inventionwill include all embodiments falling within the scope of the appendedclaims.

1. A method of forming a layered article, the method comprising:thermoforming a substrate sheet to form a shaped substrate, wherein theshaped substrate is a fiber-reinforced plastic material having a voidcontent sufficient to allow a vacuum to be applied through the shapedsubstrate; pulling a vacuum through the shaped substrate; and pulling afilm layer onto a surface of the shaped substrate to form the layeredarticle.
 2. The method of claim 1, wherein the film layer furthercomprises a compatible layer.
 3. The method of claim 1, wherein the voidcontent is greater than or equal to about 5 vol. %, based on the totalvolume of the shaped substrate.
 4. The method of claim 3, wherein thevoid content is about 10 vol. % to about 50 vol. %.
 5. The method ofclaim 4, wherein the void content is about 25 vol. % to about 50 vol. %.6. The method of claim 1, wherein the fibers have a fiber diameter ofabout 6 micrometers to about 25 micrometers, and a fiber length of about2 millimeters to about 75 millimeters.
 7. The method of claim 1, whereinthe shaped substrate is forminated.
 8. The method of claim 1, whereinthe shaped substrate is an open-celled, fiber-reinforced plasticmaterial.
 9. The method of claim 1, wherein the substrate sheetcomprises: about 25 wt. % to about 75 wt. % plastic material; about 25wt. % to about 75 wt. % fibers; and wherein weight percents are based ona total weight of the substrate sheet.
 10. The method of claim 9,wherein the substrate sheet comprises: about 35 wt. % to about 65 wt. %plastic material; and about 35 wt. % to about 65 wt. % fibers.
 11. Themethod of claim 9, wherein the plastic material is selected from thegroup consisting of polycarbonate, polyester, polyetherimide,polyphenylene ether, polystyrene, polyamide, and combinations comprisingat least one of the foregoing.
 12. The method of claim 1, wherein thesubstrate sheet is thermoformed with a membrane assisted vacuum pressureforming method with a plug-assist.
 13. The method of claim 1, furthercomprising disposing a tie-layer between the shaped substrate and thefilm layer.
 14. The method of claim 1, wherein thermoforming thesubstrate sheet further comprises heating the substrate to a temperaturesufficient to allow lofting of the fibers.
 15. The method of claim 14,wherein the temperature is about 450° F. (about 232° C.) to about 700°F. (about 371° C.).
 16. The method of claim 1, wherein the substratesheet further comprises a non-woven scrim disposed on a surface of thesubstrate sheet.
 17. A method of forming a layered article, the methodcomprising: heating a substrate sheet to a temperature sufficient toallow lofting of fibers of the substrate sheet; disposing the substratesheet against a membrane assisted pressure box; pushing the substratesheet onto a mold to form a shaped substrate; heating a film layer;disposing the film layer adjacent to the shaped substrate; pulling avacuum through the shaped substrate; and pulling the film layer againstthe shaped substrate to form the layered article.
 18. The method ofclaim 17, wherein the shaped substrate is a fiber-reinforced plasticmaterial having a void content of greater than or equal to about 5 vol.%, based upon the total volume of the shaped substrate.
 19. The methodof claim 18, wherein the void content is about 10 vol. % to about 50vol. %.
 20. The method of claim 17, further comprising disposing atie-layer between the shaped substrate and the film layer.